Solute carrier family 12 member 1 (NKCC2) (NKCC2)

Solute carrier family 12 member 1, widely known as Sodium/potassium/chloride cotransporter 2 (NKCC2), is a transmembrane protein primarily localized to the apical membrane of the thick ascending limb of the loop of Henle in the kidney (UniProt: P55017). It facilitates the electroneutral symport of one sodium, one potassium, and two chloride ions from the tubular lumen into the epithelial cells, a process driven by the sodium gradient established by the basolateral Na+/K+-ATPase. This transport is fundamental for the kidney's ability to concentrate urine through the countercurrent multiplier system and accounts for approximately 25% of filtered sodium reabsorption (PubMed: 25421528). Mutations in the SLC12A1 gene lead to Bartter syndrome type 1, a life-threatening salt-wasting tubulopathy characterized by polyuria, hypokalemic alkalosis, and hypercalciuria (NIH: GARD). Pharmacologically, NKCC2 is the target of loop diuretics such as furosemide and bumetanide, which are used to treat fluid overload in conditions like congestive heart failure, liver cirrhosis, and hypertension (StatPearls: Loop Diuretics). By inhibiting NKCC2, these drugs increase the excretion of water and salts, though they require careful monitoring due to the risk of significant electrolyte imbalances and potential ototoxicity.

Other names

Sodium/potassium/chloride cotransporter 2Bumetanide-sensitive cotransporter 1BSC1SLC12A1

Loop diuretics act as reversible inhibitors by competing with chloride ions for the chloride-binding site on the NKCC2 protein, effectively blocking the symport of sodium, potassium, and chloride ions.